La sélection du soja en France : Quel état des lieux ?

National audienceCultivated soybean [Glycine max (L.) Merr.], one of the major crops used as animal and human foods, is mainly cultivated in Argentina, Brazil, China and USA. In France, cultivated area remains low despite the interest of research and development institutes and the request of industry for non GMO seeds. After a presentation of the evolutionary history of this species, this paper is focused on the plant breeding effort realised in France in connection with research works. Special attention was paid to plant physiology knowledge development, plant stress tolerance which impacted the development of new raw material for plant breeding. The effort done by GIE Soja to continue soybean breeding programme is illustrated through 2 examples: hybridization to create new segregating populations and the improvement of seed protein content.Alors que le soja est une culture de première importance dans les échanges mondiaux, cette espèce reste peu développée en France malgré les efforts mis en oeuvre par la recherche, le développement et la demande croissante des transformateurs de graines non OGM en alimentation humaine et animale. Après avoir revu quelques traits d’histoire évolutive de cette espèce, cette présentation va s’attacher au développement de l’offre variétale en France et à la nature des programmes des recherches ayant impacté cette création variétale. Les travaux liés à la connaissance de la physiologie de la plante, à sa réponse adaptative à différents stress sont résumés. L’effort réalisé par le GIE soja pour intégrer ces connaissances afin de maintenir et améliorer l’efficience des programmes de sélection sur cette espèce est illustré à partir de 2 exemples : la création de nouvelles populations et l’amélioration de la teneur en protéines

Insights into the evolutionary history of sweet cherry (prunus avium L.)

International audienc

Reciprocal sign epistasis and truncation selection: When is recombination favorable in a pre-breeding program with a selfing species ?

Since the dawn of agriculture, humans have applied artificial selection on traits of interest, regardless of their genetic architecture. Yet, still today, most models used to study and streamline this process overlook genetic interactions. In this study, we determined the conditions in which a target genotype can be fixed when truncation selection is applied on an epistatic trait. Previous studies have shown that reciprocal sign epistasis with two fitness peaks of unequal height involves multiple equilibrium states, i.e. below one critical parameter value, such as a critical recombination rate, one genotype may be fixed, and above it, another one may be fixed. Using a haploid bi-locus model, we identified which genotype would be fixed, and how quickly, in an infinite population selected for a phenotypic trait subject to reciprocal sign epistasis with unequal peak heights, depending on two criteria: the recombination rate and percentage of selected individuals. The critical parameter values at which bistability sets in, were also calculated. These results were complemented by stochastic simulations in finite populations. Our results confirmed that, in the case of fitness under reciprocal sign epistasis, high recombination rates induce blockage at the local optimum or attainment of an equilibrium state between the two peaks. However, if linkage disequilibrium is negative in the initial population, recombination is necessary to create the most favorable genotype. Therefore, in this case, reciprocal sign epistasis favors non-null recombination rates, particularly if selection is intense

Genotyping by sequencing polyploidy wheat using RNAseq: Pitfalls and perspectives

A composite durum wheat population (Triticum turgidum, 2n=4X=28, A and B genomes) was created by crossing elite durum lines with wild (T. dicoccoides) and primitive emmer (T. dicoccum) accessions. A recessive male sterility gene was used in order to monitor the outcrossing rate in the population. Since 1997, this population is experiencing each year natural and anthropic selection with an outcrossing rate of 10 %. The EPO project aims at identifying SNPs from 100 fixed lines extracted from this important resource of diversity and to evaluate the potential of RNA seq for Genotyping by sequencing purposes. [br/] We obtained transcriptomics data for 50 individuals and built contigs using those data and standard NGS pipelines. As expected for a allotetraploid species, this first rough analysis demonstrated that for a large number of detected SNPs an excess of heterozygosity was observed. This seems to indicate that the simultaneous expression of the two A and B homeologous copies of many genes resulted in an erroneously merge of paralogous/homeologous sequences. This clearly pinpoints that such standard assembly protocols are not adapted do deal with polyploid species. [br/] We thus developed a dedicated assembly strategy that exploits strict and accession specific assemblies and Triticum monococcum and Aegilops speltoides diploids genomes to identify paralogs and homeologs in the durum wheat A and B genomes. This approach significantly increases the number of unambiguous within genome polymorphisms and offer promising perspective for genotyping by sequencing durum wheat and other polyploids of agronomic importance

Genetic diversity in a soybean collection

Contact: [email protected] audienceSoybean [Glycine max (L.) Merr.] was domesticated in China, and cultivated landraces were initially distributed throughout Asia and more recently extended to Europe and America. Previous studies of genetic diversity suggest a strong genetic bottleneck between Asian and North American soybean genetic pools. However, little is known about the potentially useful genetic diversity present in European soybean germplasm. We evaluated genetic diversity by phenotypic characterization and by comparing nuclear and cytoplasmic microsatellites in 301 genotypes of an INRA soybean collection with those of 31 European breeding lines and 17 ancestors from American cultivars (representing 83% of the North America diversity). We showed that the INRA collection contains 14 and 8% more diversity than the European breeding lines and American ancestors, respectively, based on Nei diversity (He). The genetic structure of this INRA collection does not correlate with either geographic origin or phenotypic differentiation. We generated a core collection composed of 50 accessions from the INRA collection and European breeding lines. This core collection contains 203 of the 226 microsatellite marker alleles available for this germplasm and is also representative of the diversity of morphological traits in temperate regions (maturity 000 to 111), which will be useful for future breeding program

Genetic architecture of semolina yield and of its components in durum wheat (Triticum turgidum spp. durum)

International audienc